Thursday, October 25, 2012

It's interesting. But that's not necessarily the first solution. I mean its nice to dream about in the very long term, but right now we're talking about a trip of several thousand years to get to the closest star (to say nothing of a star we'd want to get to for some other reason).

You could imagine some sort of cryogenic human payload that we could send out much slower, much smaller, and much sooner. Granted, it would take some advances in cryogenics. But I imagine that would come sooner than bending space-time (which is really what inter-stellar travel would take). Develop cryogenics, freeze some intrepid colonists, set the timer, wake them up a year or two out from their destination so they can build up strength, etc. Or better yet, unfreeze the pilot and a couple others a year or two in advance and have them - with mechanized help - set up greenhouses and shelters before waking everyone else up on the destination planet. You would need a big ship, but you wouldn't need a massive one of the sort that people usually think about for inter-stellar travel.

By the time we get cryogenics in good shape we'll probably have a much better sense of what exoplanets are "livable". Then send off a bunch of these ships and seed the galaxy with human (and presumably other terrestrial) life. If we learn how to bend space time, fine - we'll beat the popsicles to these planets. If we don't learn how to bend space-time then its good to have sent them out. And if we all kill each other here on Earth it's very good that we sent them out.

The real concern is whether they can make it: whether the cryogenics is good enough. When we're talking about settling worlds outside our solar system, it's a one way ticket. So who really cares if it happens thousands and thousands of years after you and I are dead? Who cares if these popsicles are floating through space for millenia. When they touch down what's going on on Earth is completely irrelevant.

This would be extremely expensive, of course. And you need to wait for some science to be developed. But once it is we really need to consider insurance policies like this.

What radiation problem would there be for cryogenics that there wouldn't be for a generation ship? Or do you just mean that they are getting it for millennia while a generation ship would be just getting it through a normal life time? I'd think whatever you store the bodies in could be sealed up pretty good (particularly if you do embryos as bpabbot suggests.

I'm no engineer - I'm genuinely curious. I just don't see how it could be a problem for one but not the other.

I am no engineer either, but the problem is well-known. Basically, no matter where you are, the cells in your body are always damaged by the radiation. Protons, neutrons, electrons, EM-waves of the different frequencies - when they collide with big, fragile organic molecules of the human bodies, they destroy or change them, creating cellular damage. When we are alive, we could heal that damage in no time. But when you freeze the body, you prevent all biological processes, including the ones that heal the cellular damage. By the time you unfreeze your hapless astronaut, he might be in the last stages of the radiation sickness or outright dead.

Brian Aldiss wrote a great book about a generation ship called "Non Stop", it begins:"An idea, which is man-conceived, unlike most of the myriad effects which comprise our universe, is seldom perfectly balanced. Inevitably, it bears the imprint of man's own frailty; it may fluctuate from the meagre to the grandiose. This is the story of a grandiose idea.

To the community, it was more than an idea: it became existence itself. For the idea, as ideas will, had gone wrong and gobbled up their real lives."

It's interesting to think about what working cryogenics would do to society. Imagine if, at low cost, people could have themselves frozen and wake up hundreds of years hence when technology is vastly more advanced. Think about how that would change economics. The interlinking of renewable phsyical resources, the time-preference and productivity theories of interest are what's interesting here.

Couldn't the ship just accelerate and reach near-c velocity over the course of (say) 3 years, travel to the star system, and then decelerate for 3 years before orbiting the target planet? Then maybe the people age 7 years?

Well right but I'm assuming we'll get decent cryogenics before we get that fast. But I don't know - maybe that's in the cards.

Assuming we are not going to develop propulsion technology that fast, I've just always been curious about why it's the massive star-ship idea that gets all the attention. It's romantic in a Noah's ark kind of way. But it seemed like other options might make sense to work on first.

To accelerate 1000 kg (1 metric ton) of mass to only 0.5 times the speed of light takes ~1.4 * 10^19 Joules which is the yearly electricity output of the US. To accelerate to 0.9 times the speed of light would take ~10 times more energy. Decelerating would take the same energy as accelerating.

See http://galileo.phys.virginia.edu/classes/252/energy_p_reln.html for the equation I used.

Uhh... You go to see your doctor. He says you have a heart condition, it should be operated on; but the odds that an operation performed this month will actually work are pretty poor, medicine just isn't that advanced, what we should do post-op isn't clear, the follow up drugs are still being developed and evaluated. You really ought to have that operation, but you'd be better off yet if you went into cold sleep and woke up for operation in ten years.

We can find a use for cryogenics now, I'm trying to say. And of course, it would be terribly expensive and it wouldn't work for everybody, but....

We can probably get cryogenics good enough for starships within a century, certainly within 2 centuries.

What point in sending a few people to the stars? Much easier for us to build floating colonies in the asteroid belt and even that may not be worth the sacrifice for the many on Earth to support a few in space.

If the colonists do get to a "liveable" planet it will not actually be liveable when they arrive. They will have to seed the planet with life (bacteria, plankton, lichens etc) and let photosynthesis make the planet habitable. It will be thousands of years (at least) before there will be breathable air. If you really wanted to move colonists to another world you should keep them frozen in orbit for thousands of years after arrival while robots gradually introduce life to the planet.

I once wrote a short story for my own amusement where a disaffected, and infected, alien flung his own bacteria laden frozen excrement into deep space and wound up seeding the Earth with life millenia later when the frozen excrement fell on earth. Same general process.

Oh why not? Make the reasonable assumption that technology will continue to progress and that our economic/material wealth grows apace. Then at some point it must surely be the case that colonies in the asteroids and farther out will become possible and even affordable without unreasonable "sacrifice." Consider, for example, the lot of present day Antarctic researchers compared with their predecessors a century ago. We support dozens of people at the South Pole today, year round, and it's been many many years since I've heard of taxpayers who were upset by the expense.

Beyond that... it's reasonable to anticipate (or at least hope) that progress will eventually make ALL of us reasonably healthy, affluent, and satisfied with our existence. Shall we continue then to fight religious wars, battle for economic resources, and struggle between social classes, with no other options, for the next several hundred million years on the grounds that no alternative is conceivable? Or should we, in the adulthood of the human species, persue objectives which are difficult and demanding -- such as starflight?